1. Field of the Invention
The present invention relates to an appatatus for inspecting a determined fine pattern formed on a substrate and detecting defects present therein, and more particularly to an apparatus for inspecting whether a pattern transferred on a mask or a reticle in an integrated circuit manufacturing process is correctly formed in comparison with the design data for forming said pattern.
2. Description of the Prior Art
For such purpose there has conventionally been proposed an inspecting method of comparing plural chips of the same pattern formed on the same mask, or a method of developing the design data in an image memory in the form of a bit pattern and comparing said pattern in pixel units with the image data obtained from a pattern on the mask or the reticle. However the former method based on the comparison of chips is unable to locate defects common to all the chips, and is not applicable to the inspection of a reticle pattern used as an original for preparing masks since the reticle usually contains only one pattern. On the other hand the latter method, being based on the comparison with the design data for pattern preparation, is capable of identifying defects common to the chips and is applicable to the inspection of a reticle pattern. However this method requires an image memory of a very large capacity in order to store the design data converted into the form of pixel units, and also requires a long time with a large complicated apparatus.